Circulation of group A rotavirus subgroups and serotypes in Pune, India, 1990-1997.

Group A rotavirus-positive stool specimens, collected from 432 hospitalized patients of all age groups with diarrhoea during 1990-1997 from Pune, India, were characterized for subgroups (SGs) and G serotypes (1, 2, 3, 4, 6, 8, and 10). ELISA for subgrouping was carried out by employing subgroup I and II-specific monoclonal antibodies (MAbs). For serotyping, MAbs against G1 (Ku), G2 (S2), G3 (Yo), and G4 (ST-3) were used. In addition, MAbs against G3 (RV-3), G8 (B37), G6 (bovine U.K.), and G10 (B223) were also employed. Of the 432 specimens, 174 (40.27%) belonged to subgroup I, 187 (43.29%) to subgroup II, 15 (3.47%) to subgroup I and II, and 56 (12.96%) did not react to MAbs specific to subgroup I and subgroup II MAbs. Of the 432 specimens, 111 (25.69%) reacted to one of the MAbs used. Thirty-five of the 111 specimens were serotyped as G1, 34 as G2, and 42 as G3, G4, G6, G8, and G10. Sixty-seven (21%) specimens gave dual reaction mainly to MAbs against G6, G10; G2, and G4, and in several other combinations. Forty-seven specimens (10.88%) showed multireactivities. A large number of specimens (47.92%) did not show any reactivity with MAbs employed in this study, and remained non-serotypeable. Subgroup I was found to be more common in Pune, and most specimens negative for subgroup I and II were non-serotypeable. The results implicate the need for characterization of unusual and non-typeable strains before undertaking any rotaviral vaccine studies in India.

Loss of virus specific epitopes on JE virus 'E' glycoprotein by acetone treatment.

BACKGROUND & OBJECTIVES: Some Japanese encephalitis (JE) virus strains have been placed in group II based on the loss of reactivity against Hs (H = HI positive; s = JE virus specific) group of monoclonal antibodies (MAbs) in haemagglutination-inhibition (HI) test employing sucrose acetone (SA) extracted antigens. Also acetone-fixation of cells infected with some of the virus strains results in the loss of immunofluorescence (IF) against virus specific MAbs. The present study was undertaken to elucidate the effect of acetone on virus specific haemagglutination (HA) epitopes expressed on 'E' glycoprotein of group II strains of JE virus. METHODS: Porcine kidney (PS) cells were infected with JE virus strains (2 group I Indian strains, 5 group II strains and one neutralization-escape variant of 733913 group I strain). HI and complement fixation (CF) tests were carried out employing both polyethylene glycol (PEG) precipitated and SA extracted antigens of JE virus. RESULTS: Employing PEG precipitated antigens, Indian strain G9473 showed titres ranging from 1:40 to 1:160 against all the four virus specific HsMAbs and strain 641686 (1:160) with one of the four MAbs (Hs-1) by HI test whereas their SA extracted antigens did not react at all. In contrast, CF was positive employing both SA and PEG antigens in the presence of all four HsMAbs. The reactivity shown by PEG antigens in the HI test was confirmed by blocking the HA activity with the respective MAb. SA antigens, though negative in the HI test, were positive by the blocking assay. Interestingly, some of the non-HI MAbs which were negative against SA antigens, showed positive HI reaction with PEG antigens. Also, additional epitopes on Japanese (Yoken), Sri Lankan (691004) and two Indian (755468 and 641686) JE virus strains were detected either by blocking HA or surface IF. INTERPRETATION & CONCLUSIONS: It seems that the acetone treatment might result in HA property of the antigen which is no longer inhibited by an antibody in the HI test. The characterization of such labile and conformation-dependent epitopes is currently been undertaken to elucidate their role either in protection or immunopathogenesis of JE.

Serological response to Japanese encephalitis vaccine in a group of school children in South Arcot district of Tamil Nadu.

A trial with Biken Japanese encephalitis (JE) vaccine made in Japan was carried out in South Arcot district of Tamil Nadu state, India. A total of 113 school children were included in the trial. The efficacy (as determined by serological response) and safety of the vaccine were evaluated. Side effects, though minor, were noted in 54.9 per cent of the children after each dose. The serum antibody titres were determined by mouse neutralization test, plaque reduction neutralization test and haemagglutination inhibition test. An antibody response to two-dose primary vaccination schedule was observed in 72.7 per cent, whereas 87.8 per cent of the vaccines responded positively after the booster dose administered one year after. Only about 20 per cent of the children had persisting antibodies one year after the primary vaccination. The results indicated a probable need of the third dose in the primary vaccination schedule.

Selection of a neutralization-escape variant strain of Japanese encephalitis virus using monoclonal antibody.

An Indian strain of Japanese encephalitis virus (JEV), 733913, a human isolate from Bankura, West Bengal in 1973, with all the functional epitopes designated by a panel of murine monoclonal antibodies (MAbs), was treated with one of the JEV specific HI reactive MAb(Hs-I). This led to selection of a neutralization-escape variant which showed loss of reaction to three different MAbs belonging to the same domain (Hs) and assumed similar characteristics to another JEV strain (755468) also isolated from Bankura in 1975 from mosquitoes. It is possible that selection of such variant might occur in presence of pre-existing JE antibody (Hs-I type) in pigs which are amplifying hosts of JEV. Subsequent dissemination of such variant virus could occur through mosquitoes.